Algebraic Expression
An algebraic expression is a mathematical phrase that
can contain ordinary numbers, variables (like x or y) and operators
(like add,subtract,multiply, and divide).
Here are some algebraic expressions:

a + 1

a - b

3x

x - a / b

In the above expression the "/" means divide. The "3x" means multiply the
variable x by 3.

Many english phrases translate directly into algebraic expressions, as
shown in the following table (where x stands for "a number"):

English expression

Algebraic expression

A number plus eight

x + 8

four less than a number

x - 4

half of a number

x / 2

If you set an algebraic expression equal to something, with an equal sign, you
now have an equation, like:
X - 4 = 10
To learn more about expressions, see the notes on expressions.